1. Field
The following description relates to methods of printing holographic 3D images.
2. Description of Related Art
Recently, interest with respect to 3-dimensional (3D) stereoscopic images has been growing. As a result, development of display apparatuses configured to embody 3D stereoscopic images has increased. Research is being conducted regarding embodiment of real and natural stereoscopic images based on multi-view images. For example, when a number of view points increases, stereoscopic images become more natural, but deteriorate in quality. Therefore, since a hologram recording material has the ability to embody high-quality, real, and natural stereoscopic images, the printing of holographic 3D images is being researched.
FIG. 1 is a schematic view illustrating an example of a general holographic 3D image printer. Referring to the example illustrated in FIG. 1, the general holographic 3D image printer includes a light source 10, an optical system, a printer head, and a hologram recording material 50. Here, the optical system includes a beam splitter 40, reflection mirrors 12 and 22, and lenses 23 and 24. The printer head includes a spatial light modulator (SLM) 30 and an object lens 25. Here, the light source 10 includes red, green, and blue laser light sources 10R, 10G, and 10B.
In an example, light of a predetermined color from the light source 10 is split into a reference light 11 and a material light 21 by the beam splitter 40. The reference light 11 is incident to a predetermined location on the hologram recording material 50 via the reflection mirror 12. Further, the material light 21 is incident to the SLM 30, on which color data regarding a predetermined color is displayed, via the reflection mirror 22 and the lenses 23 and 24. The material light 21 modulated by the SLM 30 passes through the object lens 25 and is incident to the hologram recording material 50. Here, an interference pattern between the reference light 11 and the material light 21 is printed on the location at which the reference light 11 and the material light 21 are incident to the hologram recording material 50. Accordingly, when respective interference patterns for three colors, e.g., red light, green light, and blue light, are printed on the hologram recording material 50, a voxel 60, which is a unit of a 3D stereoscopic image, is formed.
The voxel 60 is a pixel in 3D space, or a volume pixel including graphic data that defines unit volume in 3D space. When the hologram recording material 50 is moved in the x-axis direction or the y-axis direction to print the interference patterns on the hologram recording material 50 in correspondence to all locations of an actual 3D image, a voxel 2-dimensional (2D) array configuration, in which a plurality of voxels 60 is 2-dimensionally arranged, is formed on the hologram recording material 50.
As described above, the general holographic 3D image printer forms the plurality of voxels 60, including graphic data regarding an actual 3D image, on the hologram recording material 50. Here, the voxels 60 include graphic data corresponding to different locations of an actual 3D image, respectively. In an example, each of the voxels 60 generally includes color data of three or more colors.
FIG. 2 is a diagram illustrating an example of a person recognizing a 3D image from a hologram recording material 50 printed by the general holographic 3D image printer illustrated in FIG. 1. Referring to the example illustrated in FIG. 2, a reference light used to record a hologram to the hologram recording material 50 is irradiated to recover a 3D stereoscopic image from the hologram recording material 50 at which a voxel 2D array configuration consisting of the plurality of voxels 60 is formed.
FIG. 3 is a diagram illustrating an example of a general voxel 2D array configuration formed on a hologram recording material 50. Referring to the example illustrated in FIG. 3, while not limited thereto, each of the voxels 60 include red R, green G, and blue B color data. Here, the voxels 60 of the general voxel 2D array configuration include different pieces of location data.
FIG. 4 is a flowchart illustrating an example of a method of forming the voxel 2D array configuration as illustrated in FIG. 3. Referring to FIGS. 1 and 4, after color data regarding red color of a predetermined location of an actual 3D image is displayed (71) on the SLM 30, the red laser light source 10R emits red light that passes through the SLM 30, and records (72) color data regarding red color on the hologram recording material 50. After color data regarding green color of a predetermined location of an actual 3D image is displayed (73) on the SLM 30, the green laser light source 10G emits green light that passes through the SLM 30, and records (74) color data regarding green color on the hologram recording material 50. Next, after color data regarding blue color of a predetermined location of an actual 3D image is displayed (75) on the SLM 30, the blue laser light source 10B emits blue light that passes through the SLM 30, and records (76) color data regarding blue color on the hologram recording material 50. Therefore, the voxel 60, including red, green, and blue color data regarding a predetermined location of an actual 3D image, is formed on the hologram recording material 50.
Next, after the hologram recording material 50 is moved in the x-axis direction or the y-axis direction by the size of a voxel, the voxel formation as described above is performed. According to the example illustrated in FIG. 3, by repeating the voxel formation and the movement of the hologram recording material 50, the voxel 2D array configuration, in which the plurality of voxels 60 is 2-dimensionally arranged, is formed on the hologram recording material 50. Here, the voxels 60 include color data regarding three colors corresponding to different locations of an actual 3D image.
As described above, in a general method of printing a 3D image based on a holographic 3D image printer, a red light, a green light, and a blue light are sequentially emitted, and the SLM 30 displays respective data corresponding to the colors. As a result, color data regarding the three colors is recorded to a same voxel 60 of the hologram recording material 50 in the form of a hologram.
However, the recording process may be lengthy to complete and a brightness of a 3D image is reduced due to deterioration of diffraction efficiency (DE) of a hologram. For example, a modulated refractive index of the hologram recording material 50 is from about 10−3 to about 10−1, where the modulated refractive index is closely related to DE. In a general voxel 2D array configuration, the modulated refractive index is recorded to the voxel 60 of FIG. 3 for each of the colors. As such, modulated refractive index per color of the general voxel 2D array configuration decreases.